1. Field of the Invention
The present invention relates to a method and apparatus for separating whole blood into components thereof and for automatically collecting one of the components.
2. Description of the Prior Art
Heretofore various method and apparatus have been proposed for separating whole blood into at least three components thereof in a centrifugal liquid processing apparatus where a rotor assembly having a container for receiving the whole blood to be processed by centrifugation is rotated in the apparatus to cause separation of the whole blood into red blood cells at the outer radius, a buffy coat of white blood cells at an intermediate radius and plasma containing platelets at an inner radius of the container. Outlets are provided on the container at the different radii and tubings are connected to the outlets. Pumps are provided for withdrawing each of the blood components which collects at one of the radii and at a zone adjacent each of the outlets. The outlets are coupled to the tubings either directly or by means of a fluid seal. When they are connected directly, twisting is prevented by reason of the rotor assembly being driven at a speed twice the speed of a coaxial member mounting a cable holding device through which the tubings pass to reach the bowl in the rotor assembly. As a result of the different speeds of the coaxial member and the rotor assembly, twisting is prevented. A further explanation of an apparatus having such an arrangement and operation can be found in U.S. Pat. No. 3,986,442.
As the whole blood is centrifuged, red blood cells are being withdrawn by one pump, white blood cells are withdrawn by another pump and plasma containing platelets is being withdrawn by still another pump. The rates of withdrawal by the various pumps depend upon the concentration of these components in the blood and upon changes in the radius at which these components collect during centrifugation. Since the radii at which these blood components congregate varies during centrifugation, an operator must carefully observe the blood components while they are being withdrawn. For example, when a buffy coat of white blood cells is being withdrawn, the operator must check to see that it is not too light, i.e., plasma being withdrawn with the buffy coat, or is not too dark, i.e., red blood cells being withdrawn with the buffy coat. If the buffy coat is too light or too dark the operator will then adjust the speed of a red blood cell pump in one direction and adjust the speed of a plasma pump in the opposite direction. In other words, one will be increased in speed and the other decreased in speed so that a desired composition or optical density of the buffy coat is withdrawn. This requires constant attention by an operator and is somewhat tedious when the processing extends up to an hour or more.
As will be described in greater detail hereinafter, the present invention overcomes this operator monitoring requirement by providing a method and apparatus wherein the composition or optical density of the buffy coat of white blood cells being withdrawn from a centrifuge device is automatically monitored and when changes occur therein an optical sensing device is operable to cause an adjustment in the rates of withdrawal of the red blood cells and the plasma containing platelets so as to maintain a desired composition or optical density of the white blood cells being withdrawn.